This invention relates to a monopole antenna and, more particularly, to a disc-loaded monopole antenna which is mounted on a ground plane and is smaller than a wavelength of operation.
A monopole antenna having dimensions smaller than a wavelength of operation is useful in situations requiring an omnidirectional radiation pattern, and fairly close impedance matching to a line over a large bandwidth. In a common form of construction, such an antenna is mounted on a ground plane which serves as an element of the antenna in establishing the radiation pattern. Particular utility of such a construction is found in situations wherein the antenna is mounted on an exterior electrically conductive surface of a vehicle such as an aircraft, for transmission and reception of electromagnetic signals, and wherein the exterior surface of the aircraft serves as the ground plane.
It is desirable, in the case of vehicular communication, to minimize the size of the antenna, to provide a uniform antenna radiation pattern, and to operate over a large bandwidth with minimum standing wave ratio (VSWR).
In general, such antennas are described in Harold A. Wheeler's article entitled "Small Antennas," IEEE Transactions on Antennas And Propagation Vol. AP-23, No. 4, pages 462-469, July, 1975.